Species composition of the biospere


  • Intricate webs of interacting organisms
    • 2,000,000 species are known
    • ~18,000 plants & animals discovered yearly
    • estimated 87% of Eukaryotas unknown


  • Current composition reflects billions of ways organisms have adapted, over and over, to a changing planet


  • Humans have altered 75% of ice-free surface
    • alters species composition

“Essay of the geography of plants” by Humboldt, 1817

Uneven distribution of plants….

Humboldt lessons: Species are spatially arranged

Humboldt lessons: Species are spatially arranged

Similar biological communities reside within our biomes

Climate drives broad distribution of terrestrial biomes

Biomes have distinct soil types

Species distribution varies widely within biomes

Seasons may impact species distributions

Migration can cross many biomes: Birds

Species may also be adapted for seasonal habitats

Niche defines the limiting factors for a species

Ecological Niche =

Tolerance Ranges: Coral Reefs

Ecological niches exist in n-dimensions (many factors)

Distribution of species within biological communities overlap

Fundamental vs Realized Niche =

Species distributions are related to their realized niche space

Niches often overlap for different species

Species ranges versus distribution: Crocodiles

Species ranges versus distribution: Crocodiles

Ranges versus distribution: Plants

dispersal: movement of individuals or gametes
seed dispersal: gravity, wind, ballistic, water, and by animals

Species ranges versus distribution: Coconut tree

Biogeography and species ranges: Alfred Wallace 1859

Zoogeographic regions: Wallace